Abbreviations, to be used herein and meanings thereof are as follows.
K4CP: Chondroitin synthase derived from Escherichia coli K4 strain (serotype O5:K4(L):H4, ATCC 23502)
GalNAc: N-acetyl-D-galactosamine
GlcUA: D-glucuronic acid
SDS: Sodium dodecyl sulfate
SDS-PAGE: Sodium dodecyl sulfate-polyacrylamide gel electrophoresis
UDP: Uridine 5′-diphosphate
Patent Document 1 discloses a chondroitin sulfate synthase derived from Escherichia coli K4 strain and a DNA encoding the synthase. Patent Document 2 discloses a modified enzyme having a substitution of one or several amino acids in a certain region of K4CP (SEQ ID NO:4).
However, both of the documents do not disclose and suggest the polypeptide of the present invention, nucleic acid encoding the polypeptide, crystal of the polypeptide of the present invention, and the like. In addition, any one of the documents does not disclose and suggest ideas of modifying K4CP (SEQ ID NO:4) to increase the expression level from its DNA, to enhance the enzymatic activity, and to facilitate crystallization.
Patent Document 3 discloses a novel chondroitin sulfate lyase derived from Proteus vulgaris and a crystal thereof. However, there is no disclosure or suggestion on K4CP (SEQ ID NO:4).    Patent Document 1: JP 2003-199583 A    Patent Document 2: JP 2005-65565 A    Patent Document 3: JP 10-262660 A